The frog orchid has long been considered to be the only species in the genus Coeloglossum, although some recent classifications are regarding it as part of the larger genus, Dactylorhiza. So, some sources call it Coeloglossum viride, others Dactylorhiza viridis.
Under either name, the species has a wide distribution across the cooler parts of the Northern Hemisphere, covering much of Europe, non-tropical Asia (Russia, Japan, China, the Himalayas, etc.), much of Canada and parts of the United States (Alaska, Northeast, the Appalachians, Great Lakes Region, Northern Great Plains, and Rocky Mountains). It is typically found growing in moist, rich soil in wet meadows, moist or wet deciduous woods and thickets, and is frequently found on steep slopes.
Plant arises from fleshy, forked roots and ranges in height from 10–55 cm. The leaves of C. viride are 5–14 cm long and 2–7 cm wide; leaves at the base of the orchid are obovate to elliptical, while leaves higher on the stem become lanceolate. Two to six leaves are found on one plant, and leafing is alternate.
Inflorescence of the orchid is a dense raceme (spike-like cluster) containing 7 to 70 small flowers. Flowers are greenish in color, and often tinged with purple, reddish, or red-brown color. Flowers are subtended by conspicuous long, tapering bracts which are 1–6 cm long, with the lower bracts longer and typically greatly exceeding the length of the flower. Sepals are oval with little or no point, 3–7 mm long and 2–4 mm wide and dark green. Sepals join with petals to form a hood opposite the lower petal of the flower. Petals are long and narrow, 3.5–5 mm long and about 0.5 mm wide, and curve inwards. The lower petal is strap-shaped and usually split at the very tip to form two or three tooth-like divisions, with the middle tooth smaller than the others. It is 5–11 mm long and 1–4 mm wide. A 2–3 mm long nectar spur projects behind the labellum.
Coeloglossum viride can be mistaken for Platanthera flava (the pale green orchid), but can be best distinguished by the labellum, which is notched at the apex and does not have the tubercle of P. flava.
- Bateman, R.M. (2009). Evolutionary classification of European orchids: the crucial importance of maximising explicit evidence and minimising authoritarian speculation. Journal Europäischer Orchideen 41: 243-318. [as Dactylorhiza viridis]
- Flora of North America, v 26 p 580, Coeloglossum Hartman, Handb. Skand. Fl. 329. 1820.
- Flora of China v 25 p 117, 凹舌掌裂兰 ao she zhang lie lan, Dactylorhiza viridis (Linnaeus) R. M. Bateman, Pridgeon & M. W. Chase, Lindleyana. 12: 129. 1997.
- "World Checklist of selected plant families". Apps.kew.org. Retrieved 2013-06-03.
- "World Checklist of selected plant families TDWG Geocodes" (PDF). Retrieved 2013-06-03.
- Biota of North America Program, 2013 county distribution map
- Altervista Flora Italiana, Celoglosso Long Bract Frog Orchid, Coeloglossum viride (L.) Hartm., Accepted name: Dactylorhiza viridis (L.) R. M. Bateman, Pridgeon & M. W. Chase includes European distribution map
- "NPWRC :: Aquatic and Wetland Vascular Plants". Npwrc.usgs.gov. 2013-02-02. Retrieved 2013-06-03.
- "Coeloglossum viride (L.) Hartm. var. virescens (Muhl.) Luer". Botany.wisc.edu. Retrieved 2013-06-03.
- "Coeloglossum viride: UW-Stevens Point Freckmann Herbarium: Plant Details Page". Wisplants.uwsp.edu. Retrieved 2013-06-03.
- Ma B, Li M, Nong H, Shi J, Liu G, Zhang J.,"Protective effects of extract of Coeloglossum viride var. bracteatum on ischemia-induced neuronal death and cognitive impairment in rats." Behav Pharmacol. 2008 Jul;19(4):325-333
- Media related to Dactylorhiza viridis at Wikimedia Commons
- Data related to Dactylorhiza viridis at Wikispecies
- Coeloglossum at the Encyclopedia of Life
- Den virtuella floran - Distribution
- Acta Plantarum